Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.52	8.547%	$165.5559	$165.56	$165.55	$165.60
Purchase #2	$20.98	8.648%	$22.7944	$22.79	$22.80	$22.80
Purchase #3	$122.86	7.660%	$132.2711	$132.27	$132.25	$132.30
Purchase #4	$126.32	13.503%	$143.377	$143.38	$143.40	$143.40
Purchase #5	$181.54	3.487%	$187.8703	$187.87	$187.85	$187.90
Purchase #6	$223.79	13.222%	$253.3795	$253.38	$253.40	$253.40
Purchase #7	$177.47	6.554%	$189.1014	$189.10	$189.10	$189.10
7 purchase totals =	$1,005.48		$1,094.3496	$1,094.35	$1,094.35	$1,094.50